The present invention relates to an optical fiber array formed by fixing a glass fiber section at the end of an optical fiber to a substrate.
Generally, an optical fiber array has a V-groove substrate 25 having a V-shaped groove 26 and a lid substrate 24 to be unified with the V-groove substrate 25 as shown in FIG. 7, and has a structure in which an uncovered glass fiber section 22 formed at the end of the optical fiber 21 is disposed on the V-shaped groove 26 of the V-groove substrate 25, the glass fiber section 22 is pressed against the V-shaped groove 26 from the upper surface of the V-groove substrate 25 by the lid substrate 24 to fix the glass fiber section 22.
The V-groove substrate 25 has a V-groove forming portion 29 having the V-shaped groove 26 for housing the uncovered glass fiber section 22 formed at the end of the optical fiber 21 and a lower covered section housing portion 27 for housing a covered portion 23 of the optical fiber 21, the lower covered section housing portion 27 being formed to be deeper than the V-groove forming portion 29. The lid substrate 24 has a glass fiber protective portion 30 covering an upper surface of the uncovered glass fiber section 22 of the optical fiber housed in the V-groove forming portion 29 and the V groove 26, and an upper covered section housing portion 28 for housing a covered section 23 of the optical fiber therein, the upper covered section housing portion 28 being formed to be deeper than the glass fiber protective portion 30.
For the V-groove substrate 25 and the lid substrate 24, materials, such as glass and silicon, having high hardness and being hardly deformed are employed to ensure a positioning precision of the optical fiber 21. The V-groove substrate 25, the optical fiber 21, and the lid substrate 24 are combined, and a resin (not depicted) is filled in the gaps among them and cured to unitarily fasten them with one another.
By the way, as shown in FIG. 8, a conventional optical fiber array has a structure in which a starting point P.sub.2 of the upper counter-sunk proceeding from the glass fiber protective portion 30 to the upper covered section housing portion 28 is present above in an almost perpendicular direction (direction of a thickness of the substrates) of a starting point P.sub.1 of the lower counter-sunk proceeding from the V-groove forming portion 29 to the lower covered section housing portion 27. In an optical fiber array having such a structure, a stress due to thermal expansion or thermal shrinkage of resin or a tensile stress applied to the optical fiber from the outside is prone to concentrate in a portion between the starting point P.sub.1 of the lower counter-sunk and the starting point P.sub.2 of the upper counter-sunk.
Further, upon producing an optical fiber array, the core glass fiber section 22 is prone to be damaged by an edge portion of the starting point P.sub.2 of the upper counter-sunk when the glass fiber section 22 is pressed against the V groove 26 by the lid substrate 24. Since the damaged portion corresponds to the portion where the stress concentrates, it is apprehended that a crack is extended from the damaged portion by tensility of the fiber or a heat cycle and that the fiber is easily fractured. Further, since a fracture strength is seriously influenced by the size of the damage, products have variance in fracture strength and it is difficult to stabilize the quality of the products.